1. Field of the Invention
This invention relates to an end assembly for connection to an end of an overhead ground wire incorporating an optical fiber cable therein.
2. Prior Art
An overhead ground wire of the type described comprises a protective tube, an optical fiber cable housed in the protective tube, and a plurality of ground wire elements helically wound around the protective tube to form a wire layer of a hollow configuration. One conventional end member for connection to an end of the ground wire for connecting the ground wire to a support construction such as a pylon and a tower, as disclosed in Japanese Utility Model Application Laid-Open (Kokai) Nos. 56-171523 and 57-15630, comprises a tubular compression sleeve of metal having a uniform inner diameter. For connecting the ground wire to the support construction, the compression sleeve is fitted on the end of the ground wire and is then compressed to be deformed radially inwardly into firm locking engagement therewith. Then, the connecting sleeve is connected to the support construction by a suitable fastening means to hold the ground wire in the air. This conventional end member has been found disadvantageous, however, in that upon compression of the compression sleeve, the protective tube tends to be deformed or crushed to damage the optical fiber cable received therein since the protective tube comprises a relatively thin, soft aluminum tube.
In order to overcome this difficulty, it has been proposed in Japanese Utility Model Application Laid-Open (Kokai) No. 55-181205 and Japanese Utility Model Publication No. 58-54826 to first press-fit a crush-prevention tube of a rigid material, such as steel, in between the wire layer and the protective tube at the end of the ground wire, and to then fit the tubular compression sleeve on the end of ground wire, and to compress the sleeve in a manner described above. With this method, the protective tube is prevented from becoming crushed. The hollow wire layer around the protective tube has a generally uniform outer diameter along its length, and the compression sleeve to be fitted on the wire layer also has a uniform inner diameter along its length. Therefore, it is necessary that the compression sleeve and the crush-prevention tube should be long enough to ensure a sufficient locking engagement of the crushed sleeve with the ground wire. Thus, the compression of the sleeve of such a length requires considerable time and labor. In addition, a great pushing force has to be applied to the crush-prevention tube of such a length to press-fit it in between the the wire layer and the protective tube. Therefore, a special tool is required to push the crush-prevention tube into position.
Another form of the conventional end assembly as disclosed in Japanese Utility Model Application Laid-Open No. 56-166672 serves as a joint between two ground wires and also comprises a compression sleeve to be fitted on one ends of the two ground wire at opposite ends thereof, and a pair of crush-prevention tubes each to be press-fitted in between the wire layer and the protective tube at the end of a respective one of the two ground wires. For effecting the joint, the compression sleeve is compressed at the opposite ends thereof in a manner described above. This conventional end assembly suffers from the same disadvantages as the aforesaid prior art end assemblies suffer.